System of wireless telephony.



W. HARRISON.

SYSTEM OF WIRELESSTELEPHONY.

APPLICATION FILED OCT-30.1914- Patented Feb. 19, 1918.

VVALT'ON HARRISON, OF NEW YORK, N. Y.

SYSTEM OF W'IRELESS TELEPHONY.

Specification of Letters Patent.

Patented Feb. 19, 31918.

Application filed October 30, 1914. Serial No. 869,361.

To all whom 2'1- may concern:

Be it known that 1, emon Harrison, a citizen of the United States, residing in the city of New York, borough of Manhattan, in the county and State. of New York, have invented certain Improvements in Systems of Wireless Tele hony, of which the following is a specification.

My invention relates to telephony by means of electromagnetic waves, usually designated Hertzian waves, my general purpose being the accomplishment of a number of distinct objects, among which are the following:

I. T 0 provide an oscillating circuit, somewhat analogous to the Duddell singing arc circuit, but having, a low-resistance transmitter provided with a normally closed contact for the twofold office. of starting the oscillations and impressing them with characteristics analogous to sound waves; said transmitter thus taking the place of the arc of the lluddell circuit and also supplanting the microphonic transmitter as vheretofore inductively or otherwise connected there with.

H, To enable the condenser, heretofore considered essential in the singing arc cir cult, to be discarded altogether or temporarily disconnected, as the case may be,the function of the condenser being performed by the antenna and the earth. acting inductiyely upon each other like the coatings of an immense Leyden jar.

Ill. To dispense with much, if not praclly all. of the added inductance hereto .5 re considered essential as one of the con stants of the singing arc circuit in order to develop oscillations therein.

If. To conserve the electric current employed in producing; the oscillations. and, other factors being equal. to increase the c'llicicncy of a given amount of power used, by avoiding the waste incidental to repeatedly charging and discharging a condenser fm'inii'ig no part of the antenna.

V. To enable the use of unusually low voltages for the generation of oscillations and the consequent production of electro* magnetic wares.

Vl. To greatly simplify the wireless tcleplan and yet increase its practicability, while reducing its cost.

Figure 1 is a diagram of the terminal mechanism, which in this instance serves the purpose of both a transmitting and a receiving apparatus.

Fig, 2 is a vertical central section through one type of low-resistance microphone forming a part of my system.

At 1 is a source of electricity such as a primary or a storage battery. From it a wire 2 leads to a choking coil 3, and connected to the latter is a wire 4. A wire 5 leads from the coil 3 to the vertical antenna wire 6. Gonnected'with this wire is a grid 7 made up of a number of parallel wires disposed horizontally and spread apart, the wires 6, 7, together constituting the antenna, which is supported by masts 8, 9. The antenna as .a whole has considerable electrostatic capacity, and also much inductance, residing mainly in the grid 7. This grid, being horizontal, is substantially parallel with the adjacent upper surface of the earth. The grid and the carth act induc tivcly upon each other like the coatings of a. gigantic Leyden jar, thus collectively serving as a condenser.

Connected with the wires 5, 6, is a wire 10, which leads to a microphonic transmitter 11, hereinafter described in detail. From the transmitter 11 a wire 12leads downwardly. A ground wire 13 leads from the wire 12 to the earth, which is shown at 14. Connected with the wires 12. 18 is a wire 15. and from the latter a wire 16 leads to the battery 1.

Connected with the wires 1, 5 is a switch 17, which communicates with a condenser 18. A wire 19 leads from this condenser to an inductance coil 20. A switch 21 is provided for bringing the inductance coil 20 into and out of communication with the wires 15, 16. Connected to the wire 10 is a wire 22, and similarly connected to the Wire 12 is a wire 23. Small choking coils 24, 25

are connected with the wires 22, 23 which are also connected to a telephonic receiver 26. I will now describe ,the microphone 11. A contact plate 11 is made of semi condu'cting material such as carbon, and is preferably massive and. fiat as'shown. Resting upon its upper face'is another contact plate 11", also made preferably of carbon-or other semi-conducting material. The plate 11 is slightly dished or convex in form and of massive construction. A Ll spring 11. madeof hard rubber or other appropriate re- I silient material, is provided with a thickened portion 11, ahd extending through the latter is an adjusting, screw 11, for adjusting the degree of pressure between the con tact plates 11 11 The contact plate 11 is connected to the wires 10 and 22. and the contact plate 11- is connected to the wires '12 and 23. The telephonic receiver 26 is -v thus shunted around the microphone 11, and the latter is bridged across the terminals of the battery. The condenser 18 and the inductance coil 20, in series with each other,

are also bridged across the battery termi-- nals, By opening the switches 17, 21. the condenser 18 and the inductance coil 20 may be completely disconnected from the battery. The resistance, inductance and capacity (2'. 0.. the constants) of the various wires and other conducting parts should. be distributed and apportioned so as to follow, to some extent, the analogy of the Duddell singing are circuit. That is to say, the normal ohmic resistance ofthe microphone 11 is so apportioned that its numerical value.

may be incorporated in an effective formula for producing oscillations. To this end the,

- microphone 11 is given such a low ohmic resistance'that, in any given formula for the Duddell singing arc circuit, the micro-- phone may be considered as the arc. For this purpose. the microphone may be made of any desired ohmic resistance-ranging from one-tenth of an ohm up to ten or twelve ohms or even higher--depending upon the voltage employed, the amperage available for different kinds of battery used, and also upon the numerical value of the other constants, namely, the inductance and capacity.

In apportioning the inductance and capacity of the oscillation circuit, if the me chanism is to be operated with the switches 17 and 21 closed, the capacity of the antenna should bo'considercd as coupled with the ca'pacityot' the condenser 18, and in apportioning the inductance of the circuit, the inductance of the coil 20 should be considered as coupled with the inductance of other parts, and particularly of the antenna.

When the apparatus is to be operated with the switches 17, 21 open. the condenser 18 and the inductance coil 20 are omitted from consideration. Therefore in formula: em-

ployed for determining conditions under which oscillations must take place, and for apportioning or determining the time perlod of such oscillations, the capacity of the cir- I cuit isconsidered as simply the capacity of the antenna-audits immediate connections,

consideredas in inductive relation to the adjacent surface of the earth, as mentioned -condenser 18 and inductance coil 20 be discarded or temporarily thrown out of. action,

but if oscillations of low frequency be desired, the length of this rid may be increased. a

The battery 1 may be of comparatively low voltage, if it be capable of developing considerable amperage,'.provided the resistance of the microphone 11 is also sufiiciently low. If desired, the contact plates 11, 11 or either of them, may be permeated with yarious metallic salts, as is done with lighting carbons, in order to reduce their resistance. By varying the curvature of the contact plate .11, the resistance of the microphone may be apportioned with proximate'accuracy, and by adjusting the screw 11 the resistance ofthemicrophone may be adjusted to accord with a particular calculation. Moreover, by adjustingthe'screw 11, the oscillation circuit may be attuned to some extent, independently of any tuning coil which may be employed.

The inherent instability of a low-resistance microphone of the type above described serves the purpose of starting the oscillations; in much the same manner that in the Duddell system'the oscillations are started by the inherent instability of the are.

It is desirable, though not essential, that the oscillations be of a frequency above the limit of au'dibility for acoustical vibrations. This resultis easily accomplished, especially in instances where the condenser 18 and the inductance coil 20 are thrownyout of action.

The microphone '11, besides taking the place of the Duddell are as above-described, performs two other important. functions,- namely, it serves as a telephonic transmitter and also in "some instances as a wave de-' tector. In its capacity as a transmitter it varies the power of each oscillation, and the do gree of variation thus brought about is very great owing to the fact that all of the current passes directly through the microphone.

The potential of the battery employed may be anywhere from one volt to twelve volts iii the contacting plates 11 11 of the microphonic transmitter be made of carbon as above described-the voltage varying with the purity and hardness of the carbon.

Higher voltages may be employed, however, if instead of making the plates 11, 11

of carbon they are constructed of poor conductors having ohmic resistance greater than that of carbon. In instances where such higher voltages are desired, the contact members of the microphonic transmitter may be made of silicon, molybdenite, carborundum or various crystalline minerals or salts. The contact material of the microphonic transmitter should preferably have a negative temperature coeilicient of resistance, as is the case with an arc. That is to say, the heating of the material. by the passage of the current through it, should reduce its ohmic resistance, as is the case with carbon. With such material in use a slight initial variation, from any cause. in the flow of current through the microphone 11 so alters the ohmic resistance of the latter that the current variation is amplified. The amplified variations in the flow of current set up corresponding variations in the voltage, and these variations in voltage in turn force varying quantities of current through the microphone. Oscillations are therefore in evitable if the normal, resistance of the microphone is sufiiciently low to become an admissible factor, along with any given inductance and capacity. in the Duddell formula for setting up oscillations.

When the normal ohmic resistance of the microphone is just a trifle too high to permit the spontaneous development of oscillations, and the microphone is subjected to the action of sound waves, the resulting variations in the flow of the current will set up oscillations, and these oscillations will be sustained only while the microphone is being acted upon by the sounds. During the periods while the oscillations a is thus sustained. their mean amplitude must vary in accordance with the intensity of the sound waves. Hence, under the conditions just described. electromagnetic waves are not thrown off by the antenna except, when the microphonic transmitter is subjected to the acoustical action of sound waves, and when thus thrown off they are impressed with characteristics analogous to sound waves.

The microphone in its capacity as a wave detector acts after the manner of a carbon coherer. The choking coils 24. 25 ha e sutlicient inductance to prevent the oscillations from reaching the receiver 26. The microphone isnot employed as a wave detector except in instance Where the voltage of he battery 1 is compa atively low. However, any other ware d. suitable for wireless telephony, may be employed and cond up in the usual or any desired manner. if desired, the constants (inductance, capacity and resistance) may be so apportioned that normally oscillations are not developed, but can easily be started and yet maintained diz ficulty. Such purwnn pose may be facilitated by a careful adjustment of the microphone, by means of the screw 11 This done, it the transmitter be subjected to the action of sound waves of varyingcharacter, as for instance in articulate speech, the oscillations are repeatedly started, increased, diminished, and stopped, and thus are in the aggregate impressed with characteristics analogous to sound waves. With this particular use of the device oscillations are not developed except under stimulus of the voice. The practical efiect is about the same as if the oscillations were of purely acoustical origin.

The operation of my system will readily be understood in view of the foregoing explanation. The parts being assembled and arranced as described, and the battery being in action, theoperator simply talks into the transmitter 11. The oscillations are impressed with characteristics analogous to sound waves, and thus impressed they set up electro-ma 'netic waves which travel to a distant station and there control the reprod tion of the sounds.

When the microphone i1 is employed as a wave detector, its best use is to pick up musical sounds or sounds of a comparatively low order, When speech is to be transmitted, it may be desirable to use a ,diterent kind of detect r and to connect it in the usual or any ditl'erent manner.,

The system above described is very simple in construction and action. Its various parts are easily obtained, and can be put together at a very small cost. No special skill is essential to build or operate the apparatus. The system is well adapted for house-tohouse service, or for use upon small vessels employed in coast and harbor trailic. The reduction "in the voltage required is of manifold advantage; and while such reduction in voltage would ordii'iarily mean a loss of power. my system supplies compensating advantages including increased etliciency for a given voltage.

I I do not limit myself to the particular mechanism shown. the scope of my invention being commensurate with my claims.

I claim 1. The combination of a source of electricity, a circuit connected therewith and having its constants apportionedapproxisustained oscillations from the currents sup- Fina plied from said source of electricity, and a low-resistance contact included in said circuit and normally closing the same, sa d contact having its ohmic resistance unstable for the purpose of starting said oscillations.

2. In a wireless telephone transmitting system the combination of a direct-current source of electricity, a circuit connected thereto and having its constants apportioned and arranged approxin'iately at the critical point for the development of sustained oscillations, and a solid-contact microphone included in said circuit and having its resistance normally unstable for the purpose of startingsaid oscillations.

3. in a. wireless telephone transmitting system the combination of a source of electricity, a circuit connected thereto and havinc; its constants apportioned and arranged approximately at the critical point for the development of sustained oscillations, and a low-resistance telephonic transmitter included in said circuit and having: its ohmic resistance normally unstable for the conjoint purposc'of starting said oscillations and impressing the same with characteristics'analogous to sound waves.

4. The combination of a direct-current source of electricity, a circuit connected thereto and having its constants apportioned and arranged at a point critical for the development of sustained oscillations, and a carbon microphone included in said circuit and having a 'ariable resistance controllable byjsound waves for starting said oscillations and impressing the same with variations analogous to sound waves.

5. The combination of a direct-current 6'. The combination of a directcurrent.

source of electricity, a microphone the ohmic resistance of which is unstable and comparatively low, said microphone being adapted for use as a transmitter and as a wave detector, a circuit including said source of electricity and said microphone, and having constants apportioned and arranged appr Ximately at a point critical for the development of sustained oscillations, said circuit being controllable by said microphone for the joint purpose of starting said oscillations and impressing the same with characteristics analogous to sound waves when said microphone is used as a transmitter, and a receiver connected with said microphone and energized by said source of elecface of the earth act collectively as a condenser and thus avoid the necessity for an ordinary condenser, a direct'currcnt source of electricity, acircuit includingsaid source of electricity and connected to said antenna and to the earth, the constants of said circuit inclusive of said antenna and the earth connection being apportioned and arranged for the development of sustained oscillations, and means for starting said oscillations.

8. The combination of an antenna having considerable inductance and capacity and disposed in inductive relation to the earth, a direct current source of electricity. a circuit connected with said source of electricity, and also with said antenna and the earth, the constants of said antennabeing so apportioned and arranged as to enable said circuit, independently of. the addition of a condenser, to develop \sustain-ed oscillations, and a member included in said circuit for starting said oscillations. a

9; The combination of an antenna having considerable inductance and capacity and disposed in inductive relation to the earth. a source of electricity. a circuit connected with said source of electricity and also with said antenna and the earth. the constants of said antenna being so apportioned and arranged as to enable said circuit, independently of the addition of a condenser, to develop susrained oscillations. and a carbon transmitter included in said circuit for starting said o'scill'ations and also for impressingthe same ."ith characteristics analogous to sound waves.

10. The combination of an antenna having considerable inductance and capacity and disposed in inductive relation to the earth, a direct current source of electricity, a circuit connected tosaid source of electricity and also connected to said antenna andto the earth, the constants of said antenna being so apportioned and arranged as to enable said circuit, independently of'the use of an inductance coil, to develop sustained oscillations, and means included in said circuit for starting said oscillations.

11. The combination of an antenna having considerable inductance and capacity and disposed in inductive relation to the earth, a source of electricity, a circuit conected to said source of electricity and also connected to said antenna and to the earth, the constants of said antenna being so apportioned the constants of said circuit inclusive of said antenna and the earth connection being ap-v and arranged as to enable said circuit, independently of the use of an inductance coil,-todevelop sustained oscillations, and a microphone included in said circuit for the twofold purpose of starting sa1d oscillations and impressing thereupon characteristics analogous to sound waves;

lengthy portion disposed substantially par'-.

allel With the surface of the earth and in inductive relation thereto so that said lengthy portion of said antenna and the adjacent surface of the earth act together as a condenser, a direct current source of electricity, a circuit including said source of electricity and connected to said antenna and to the earth,

portioned and arranged approximately at the critical point for the development of sustained oscillations, and means controllable by sound Waves and associated with said cir cuit for varying-the current-passing quality.

of said circuit. I

13. Ina system or Wireless telephony the combination of. an antenna having a lengthy portion disposed substant'iahyfiarallel With the surface of the eaith andp'n inductive relation thereto so that said lehgthy portion 01' said antenna and the adjacent surface of the earth act together as a condenser, a direct current source of electricity, a circuit energized by said sourcei-of electricity and connected to said antenna and to'the earth, the constants of said circuit, ihclusive of said antenna and the earth connection being apportioned and arranged vapproximately at the critical point for the development of oscillations, and mechanism for varying one of said constants in order o cause the development of oscillations impressed with characteristics of sound Waves.

14. In a system for Wireless telephony the combination of an antenna having a horizontal component disposed in inductive relation to an ad acent ortion of the earth and act- 'ing together t ereWith' as a condenser, a

source of direct current, a circuit energized by said source of direct currentand connect ed to said antenna and to the earth, the constants of said circuit inclusive of said anit'ennavand the earth connection being apporcritical point for the development of oscillations, and electric mechanism controllable by 'sound Waves and associated with sa1d circuit for the purpose of-increasing and decreasing the mean effectiveness of sa1d constant's and thereby intermittently developing oscillations impressed with characteristics of sound Waves.

15. In a Wireless, telephonic transmitter system an oscillating circuit having its constants ne'arly but not quite in' proper proportion for the development of sustained oscillations, and a telephonic transmitter inpose of starting said oscillations and imvpres sing the same With'characteristics analogous to sound Waves.

16. A system for Wireless telephony comprising an antenna having a horizontal component disposed in inductive relation to an .tioned and arranged approximately at the .cluded in said circuit for the two-fold pur- 

